Start Practice Test

Tennessee CMC-C – Mechanical HVAC/Refrigeration Contractor Practice Exam

What This Practice Exam Covers

The Tennessee CMC-C licensing exam tests HVAC/Refrigeration contractors across 10 topic areas in 100 questions, with a 260-minute time limit. You need a 73% (73 correct) to pass.

This practice site gives you two ways to prepare:

Free practice exam: 10 questions per attempt drawn from a limited question pool. There's no registration wall — take it as many times as you like to get a feel for the question style, phrasing, and difficulty level before committing to full prep.

Full practice exam (paid): 100 questions, timed at 260 minutes, drawn from a pool of 526+ questions — so every attempt produces a unique exam with no repeated sets. Questions are mapped to the same topic weights the official test provider uses, giving you the most accurate readiness signal available outside the real exam room.

Start with the free exam to benchmark yourself, then use the full exam for serious preparation.

What You'll Be Tested On

Electrical Knowledge, Motors, and Controls — 7 items
Expect Ohm's Law and its variants (watts, horsepower, kVA formulas), series and parallel circuit calculations, and reading both pictorial and ladder diagrams. Motor questions focus on split-phase, capacitor-start induction-run, capacitor-start capacitor-run, and shaded-pole motor types (Chapter 15, Section 15.2.1). Controls questions cover current relays, potential relays, positive temperature coefficient relays, solid-state relays, and high- and low-pressure motor controls (Chapter 16, Section 16.3.4 and 16.3.5). Metering with clamp-on and in-line ammeters, continuity checks, and frequency checks also appear (Chapter 17, Section 17.1.3).

Piping – Refrigeration, Hydronic, Steam and Process — 14 items
The largest topic alongside Ducts. You must know copper tube types (K, L, M), ACR tubing properties, and when each is appropriate. Expect questions on flared, soldered, brazed, and swaged connections — technique, temperature, and code compliance. Tubing cutting, bending, and pipe expansion calculations are also tested. Know how thermal expansion affects long piping runs (Expansion of Pipe per 100 Feet table).

Heating and Cooling Principles and Theory — 10 items
Gas law relationships, pressure-temperature behavior, and the compression refrigeration cycle are central. Heat transfer calculations using K-value, C-value, R-value, and U-value appear regularly. Mixed-air temperature calculations (as in the worked sample below) require weighted-average arithmetic. Understand sensible vs. latent heat, superheat, subcooling, and how each stage of the refrigeration cycle changes refrigerant state.

Heating and Cooling Equipment and Components — 10 items
Compressor types — reciprocating, scroll, screw, centrifugal — and their configurations (Modern Refrigeration and Air Conditioning, Chapter 18). Metering device types including thermostatic expansion valves, fixed orifices, and capillary tubes, and how each responds to load changes. Know compression refrigeration fundamentals at the component level: what each device does and what happens to system performance when one fails.

Refrigerants and Refrigeration — 10 items
Refrigerant classification matters here: CFC, HCFC, HFC, HFO, and hydrocarbon refrigerants, along with their ODP and GWP ratings. EPA Section 608 recovery, recycling, and reclaiming procedures are directly tested — including Type III recovery techniques for low-pressure systems. Know how to use gauge manifolds, service valves, and vacuum pumps correctly. Refrigerant cylinder safety is also covered (HVACR Textbook, Chapter 2, Section 2.2.4).

Fuel and LP Gas — 10 items
Gas piping materials, sizing, and pressure requirements draw from the International Fuel Gas Code 2021. Know combustion air requirements for gas-fired appliances (IFGC Page 3-3 to 3-4), LP gas storage and handling rules (IFGC Page 6-10, Section 630.3), and pressure regulator requirements (IFGC Page 4-48, Sections 410.2 and 410.3.1). Venting system requirements — including connector materials and clearances — also appear here.

Combustion Air, Chimneys, Flues and Vents — 10 items
Venting system sizing for Category I appliances is a tested calculation. Know vent connector materials, installation requirements, and required clearances (International Mechanical Code, Sections 801.6 and 801.7). Appliance type definitions (IMC Chapter 2) determine which venting category applies, so understand how input rating, draft type, and flue gas temperature classify an appliance.

Ducts, Ventilation and Exhaust — 14 items
Tied with Piping as the heaviest topic. Duct pressure classification drives material selection. Know leakage testing standards, sealing requirements, and where fire and smoke dampers must be installed (IMC Chapter 10, Sections 1006.4 and 1006.6). Equivalent round diameter calculations (as in the worked sample below) use the standard empirical formula and appear on this exam. IMC Chapter 11 ventilation requirements — including Sections 1108.3.1, 1108.3.3, and 1109.2.7 — also appear.

Load Calculation — 5 items
Fewer questions, but they require multi-step arithmetic. Know heating and cooling design temperature differences (HTD, CTD), how to apply U-values and CLTD to opaque assemblies, and how to calculate fenestration loads including overhang and shading adjustments. Infiltration load methods (ACH table, component leakage area, blower door) and duct system heat loss and gain factors round out this section.

Safety, Fire and Smoke Protection — 10 items
Lockout/tagout (LOTO) procedures, PPE selection, and fall protection requirements from 29 CFR 1926 are directly tested — including scaffolding safety (HVACR Textbook, Chapter 2, Section 2.4.3) and fall protection training (Section 2.4.4). Fire and smoke damper installation and ratings appear here and overlap with the Ducts topic. GHS chemical hazard communication is also covered (HVACR Textbook, Chapter 2, Section 2.2.6).

Worked Sample Questions

Question 1 — Piping

You are installing a run of hard-drawn ACR copper tubing in a commercial refrigeration system. What is the primary reason this tubing requires few clamps or supports, particularly in larger diameters?

• A. It has a heavier wall than soft tubing
• B. It is hard and stiff by nature
• C. It is sealed with nitrogen internally
• D. It is annealed after manufacturing

Correct Answer: B

Hard-drawn ACR tubing is manufactured to be rigid. That inherent stiffness — not wall thickness, not internal pressure — is what eliminates the need for frequent support spacing, especially as diameter increases. Option A is a distractor: wall thickness alone doesn't determine rigidity in the same way material hardness does. Option D is the opposite of correct; annealing softens metal, producing soft or annealed tubing, not hard-drawn. Option C has no bearing on structural support requirements.

Source: Modern Refrigeration and Air Conditioning, Page 139

Question 2 — Ducts, Ventilation and Exhaust

A rectangular duct measures 12" × 8". What is the equivalent round diameter?

• A. 10"
• B. 11"
• C. 12"
• D. 14"

Correct Answer: B

Use the standard equivalent diameter formula:

D_e = 1.3 × (a × b)^0.625 ÷ (a + b)^0.25

Plugging in a = 12, b = 8:
- a × b = 96; 96^0.625 ≈ 20.8
- a + b = 20; 20^0.25 ≈ 2.11
- D_e = 1.3 × 20.8 ÷ 2.11 ≈ 10.7 inches → rounds to 11 inches

This formula appears consistently in duct design. Candidates who estimate by averaging dimensions (getting 10") or rounding up arbitrarily miss this question. Run the numbers.

Question 3 — Heating and Cooling Principles and Theory

A rooftop unit mixes 2,000 CFM at 65°F with 1,000 CFM at 90°F. What is the mixed air temperature?

• A. 70°F
• B. 73°F
• C. 75°F
• D. 80°F

Correct Answer: B

Mixed air temperature uses a CFM-weighted average:

(2,000 × 65) + (1,000 × 90) ÷ (2,000 + 1,000)
= (130,000 + 90,000) ÷ 3,000
= 220,000 ÷ 3,000
= 73.3°F ≈ 73°F

The most common wrong answer is 75°F — the simple arithmetic mean of 65 and 90 — which ignores the fact that twice as much air enters at 65°F. Always weight by CFM, not by the number of airstreams.

How to Read Your Score

The passing threshold is 73% — that's 73 correct out of 100. On the full practice exam, treat your first attempt as a diagnostic, not a verdict. A first-attempt score in the 60s is common and tells you which of the 10 topic areas need the most work, not that you're unready to continue preparing.

A topic-by-topic breakdown is where the real information is. If you're scoring well on Electrical (7 items) but losing ground on Ducts (14 items) or Piping (14 items), those two topics alone represent 28% of the exam — fixing them has an outsized effect on your total score. Conversely, a strong showing on Load Calculation (5 items) barely moves the needle if heavier topics are soft.

Scoring 73–78% on practice generally means you're close but vulnerable to question variations. Most candidates who pass comfortably score in the low-to-mid 80s on practice before sitting the real exam. Use multiple full-exam attempts — since each draws from a 526+ question pool — to expose yourself to the full range of question phrasings before exam day.

Where Candidates Lose Points

Piping and Ducts math errors. The equivalent round diameter formula has four operations in a specific order. Candidates who approximate or use the wrong exponent get a plausible-looking wrong answer. Similarly, pipe expansion calculations require reading the correct table value and applying it per 100 feet — errors compound on longer runs.

Refrigerant classification confusion. HCFC vs. HFC vs. HFO questions hinge on ODP and GWP distinctions. Mixing these up on even two or three questions in the Refrigerants and Refrigeration topic (10 items) is a meaningful score hit.

Wrong venting category applied. Combustion Air, Chimneys, Flues and Vents (10 items) frequently tests which appliance type gets which venting treatment. Applying Category I sizing rules to a Category III appliance is a common error that cascades into wrong answers on follow-up questions.

CFR safety citation details. The Safety, Fire and Smoke Protection topic pulls from specific 29 CFR 1926 sections. Candidates who know the concept but not the specific rule (for example, confusing scaffolding requirements with ladder safety requirements) pick the wrong answer even when they understand the underlying safety principle.

Running out of time on Load Calculation. Five questions don't sound like many, but multi-step CLTD and fenestration calculations can eat 6–8 minutes each. Practice doing these under time pressure so they don't drain your clock on exam day.

Exam Quick Facts